The 1957 Major League Baseball season was played from April 15 to October 10, 1957. The National League's Brooklyn Dodgers and New York Giants played their final seasons as New York City-based franchises before their moves to California for the 1958 season, leaving New York City without a National League team until the birth of the Mets in 1962.
April 18 – New York City Parks Commissioner Robert Moses proposes a new 78-acre (320,000 m2) tract in Flushing Meadows as a site for a new National League baseball stadium. The plan, submitted to mayor Robert Wagner, includes a 50,000-seat stadium with a plastic dome to be built by the Parks Department.
April 21 – The Cincinnati Redlegs are involved in a bizarre play in a game against the host Milwaukee Braves. With Don Hoak on second and Gus Bell on first, Wally Post hits a ground ball to Milwaukee shortstop Johnny Logan. Hoak breaks up a potential double play by fielding the ball himself and flipping it to Logan. Hoak is called out for interference (contact with batted ball before a fielder touched it), but Post is given a single on the play. The day before, Johnny Temple let Bell's ground ball hit him with the same result, Temple being called out for interference and Bell being awarded a single. The two incidents prompt league presidents Warren Giles and Will Harridge to jointly announce a rule change that declared both the runner and batter out if the runner intentionally interfered with a batted ball, with no runners allowed to advance.
April 24 – The New York City Board Of Estimates fails to act on the Moses plan as outlined by Mayor Wagner.
May 7 – Cleveland Indian pitcher Herb Score is hit in the face by a line drive by New York YankeeGil McDougald, the ball breaking numerous bones in Score's face and leaving him quite bloodied. McDougald vows to quit if Score is blinded as a result. Score regains his 20/20 vision, but will miss the remainder of the 1957 season.
July 18 – Horace Stoneham states the Giants will leave New York after the season. He says he has not heard anything more from San Francisco and that his move is not contingent on that of the Dodgers. Stoneham sees a new stadium or joint occupancy with the New York Yankees as the only reason for the Giants to stay in New York.
August 19 – As Stoneham cites poor attendance as the reason for the Giants' move, the team's board of directors votes 8–1 to move to California in 1958, as San Francisco promises a new stadium in the Bayview area. The only dissenting vote is by M. Donald Grant, who would go on to become one of the founders of the New York Mets.
October 8 – Walter O'Malley announces that the Dodgers will move to Los Angeles for the 1958 season. New York would not have a National League team again until the expansion New York Mets began play in 1962.